Materials Data on Xe by Materials Project
Xe crystallizes in the orthorhombic Cmce space group. The structure is zero-dimensional and consists of eight xenon molecules. Xe is bonded in a 1-coordinate geometry to atoms.
36 MATERIALS SCIENCE↗
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Materials Data on Xe by Materials Project
Xe is alpha Samarium structured and crystallizes in the trigonal R-3m space group. The structure is zero-dimensional and consists of nine xenon molecules. Xe is bonded in a 1-coordinate geometry to atoms.
36 MATERIALS SCIENCE↗
Materials Data on Fe4AgP(XeF3)2 by Materials Project
(Xe)2Fe4AgF4PF2 crystallizes in the tetragonal I-4c2 space group. The structure is zero-dimensional and consists of four difluorophosphine molecules, eight xenon molecules, and four Fe4AgF4 clusters. In each Fe4AgF4 cluster, Fe is bonded in a distorted single-bond geometry to one F atom. The Fe–F bond length is 1.85 Å. Ag is bonded in a 4-coordinate geometry to four equivalent F atoms. All Ag–F bond lengths are 2.40 Å. F is bonded in an L-shaped geometry to one Fe and one Ag atom.
36 MATERIALS SCIENCE↗
Materials Data on Na4XeO14 by Materials Project
Xe(Na2O7)2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional and consists of four xenon molecules and one Na2O7 framework. In the Na2O7 framework, there are two inequivalent Na sites. In the first Na site, Na is bonded in a 5-coordinate geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.34–3.03 Å. In the second Na site, Na is bonded in a 4-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.26–2.98 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to two O atoms. There is one shorter (1.35 Å) and one longer (1.38 Å) O–O bond length. In the second O site, O is bonded in a bent 120 degrees geometry to two O atoms. There is one shorter (1.26 Å) and one longer (1.89 Å) O–O bond length. In the third O site, O is bonded in a distorted trigonal planar geometry to two Na and one O atom. In the fourth O site, O is bonded in a distorted T-shaped geometry to two Na and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a 4-coordinate geometry to two equivalent Na and two equivalent O atoms. In the sixth O site, O is bonded in a distorted see-saw-like geometry to three Na and one O atom. In the seventh O site, O is bonded in a distorted L-shaped geometry to two equivalent Na and two equivalent O atoms. In the eighth O site, O is bonded in a 3-coordinate geometry to two Na and one O atom.
36 MATERIALS SCIENCE↗
Materials Data on Fe4AgXeF5 by Materials Project
XeFe4AgF5 crystallizes in the tetragonal I4/m space group. The structure is two-dimensional and consists of four xenon molecules and two Fe4AgF5 sheets oriented in the (0, 0, 1) direction. In each Fe4AgF5 sheet, Fe is bonded in a 3-coordinate geometry to three F atoms. There are a spread of Fe–F bond distances ranging from 2.00–2.35 Å. Ag is bonded in a square co-planar geometry to four equivalent F atoms. All Ag–F bond lengths are 2.49 Å. There are two inequivalent F sites. In the first F site, F is bonded in a distorted T-shaped geometry to two equivalent Fe and one Ag atom. In the second F site, F is bonded in a square co-planar geometry to four equivalent Fe atoms.
36 MATERIALS SCIENCE↗
Materials Data on Xe by Materials Project
Xe is alpha La structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is zero-dimensional and consists of four xenon molecules. Xe is bonded in a 1-coordinate geometry to atoms.
36 MATERIALS SCIENCE↗
Exploring Causes of Beam Loss at CEBAF
At Jefferson Lab, the Continuous Electron Beam Accelerator (CEBAF) features a unique design with two linear accelerators and two arc sections allowing for multiple turns of the electron beam, as well as four experimental end stations. This topology leads to increased beam losses, especially in the spreader and recombiner regions connecting the arcs to the linacs and in the extraction regions connecting the experimental end stations to the accelerator. These losses result in equipment activation and operational interruptions. Recent upgrades to the facility’s diagnostic systems, including the addition of xenon ion chambers, have provided higher-resolution data regarding these loss events. Building on this improved observational capability, we are developing a simulation framework using optics codes and the Geant4-based BDSIM to model beam extinction and halo formation in these regions. This work aims to correlate simulation results with experimental data to isolate the causes of beam loss and inform future machine tuning strategies. We present a summary of conclusions drawn from recent operational studies and outline a plan to model the beam loss and validate the simulations.
Matthews, C. [Old Dominion Univ., Norfolk, VA (Uni↗
DUNE’s Potential to Search for Neutrinoless Double Beta Decay
Neutrinoless double beta decay is a forbidden process by the standard model due to a violation of lepton number and could be piece of the matter/anti-matter asymmetry puzzle. Its rarity makes it very difficult to search for, but if found could aid in figuring out the mass hierarchy. The idea is to take advantage of DUNE's size and capabilities to attempt to detect the decay by doping the liquid argon with Xenon, a candidate isotope for this decay. Thus, we need to know whether this search is feasible within DUNE’s framework
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Fission Gas Measurements in Spent Fuel: Literature Review
The fission-derived noble gases, xenon(Xe) and krypton(Kr), have long been proposed as a tool for supporting nuclear safeguards and declarations verification. A vast body of literature outlines how these non-reactive fission gases released during reactor operation and shutdowns correlate to burnup level, power history, other reactor specifications and reprocessing activities. However, irradiation conditions can vary appreciably both radially and axially within a fuel pin.
07 ISOTOPE AND RADIATION SOURCES↗
Laboratory Investigation of Gas Transport Through Variably Saturated Rock [Slides]
Project Overview: Noble gas fission products, such as xenon (Xe), are monitored to detect nuclear tests. For well-contained subsurface tests, transport to the surface will impact detected isotopic ratios, complicating event identification. Role of water saturation in subsurface transport is not well understood. Historic tests have taken place near or below the water table. To accurately predict breakthrough times and fractionation, gas transport must be characterized through intact rock with variable saturation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
nEXO Team Active Georgetown University: Systems Integration and Test
The nEXO experiment is the “next” tonne-scale enriched xenon observatory which will be fielded deep underground to search for neutrinoless double-beta decay. The observation of neutrinoless double-beta decay is important to the low-energy physics community, and confirmation of the phenomenon will allow physicists to extend current physics models and propose new theories for the evolution of matter in our universe.
42 ENGINEERING↗
nEXO Passive Signal Chain
The Next Enriched Xenon Observatory (nEXO) primary mission goal is to detect neutrinoless double beta decay, proving neutrinos are Majorana type fermions. Neutrinoless double beta decay (0vBB) is a theoretical type of radioactive decay in which two electrons and no neutrinos are emitted.
42 ENGINEERING↗
Development of a Direct Neutral Density Diagnostic for Fusion Edge Plasmas
As magnetically confined plasmas progress towards ignition and long pulse experiments, measurement and control of the neutral density in the plasma edge has become a critical issue for stability, formation of transport barriers, and fueling. Recent experiments by our research group have demonstrated that is possible to use two-photon absorption laser induced fluorescence (TA-LIF) to directly measure the density of neutral hydrogen in helicon sources and in the HIT-SI3 spheromak. While those experiments validated key elements of a diagnostic system that would enable similar measurements in tokamak plasmas, they did not fully address the issue of performance optimization in the presence of intense background light at the fluorescence wavelength and they also identified a number of other issues that must be resolved before successful TALIF neutral density measurements in a tokamak are likely to be achieved. Additional specific concerns raised during design reviews with the leadership of the DIII-D tokamak facility included: the minimum detection threshold for this TALIF diagnostic (currently ~ 5 x 10 15 m -3 ) and the rate at which neutral density measurements could be obtained. Improving the system performance to reduce the minimum detection threshold and demonstrating a faster rate of density determination are required to advance this diagnostic to the level where it could be considered for implementation on a major tokamak facility in the USA. The key issues that will be addressed through additional technological development are: validation of a new, chromatic aberration-free, xenon calibration scheme; increasing the output power of the laser; and suppression of background emission at the fluorescence wavelength through optimization of the collection optics and gating of the photomultiplier detector with a goal of obtaining a minimum detection threshold of 5 x 10 14 m -3 . Another key technological development, so far only tested in helicon source experiments, is the validation of Doppler-free TALIF as a means of obtaining higher speed, calibrated, neutral density measurements in tokamak-like conditions at the full cadence of the pulsed TALIF laser. In this work, we propose to complete these technological advancements through installation and testing of our prototype TALIF system on the proto-MPEX experiment at Oak Ridge National Laboratory (ORNL). The proto-MPEX facility will provide plasma conditions similar to the edge plasma of a major tokamak experiment but with pulse lengths and pulse repetition rates ideally suited for extensive development of a TALIF neutral density diagnostic. Measurement of the absolute neutral density in the edge of a magnetically confined plasma is necessary for plasma density control; calculation of charge-exchange power losses; control of plasma-wall interactions; determination of the braking of plasma flow; determination of the fuel mixture in deuterium-tritium plasma; and understanding the dynamics of the divertor region in the plasma edge. In terms of potential impact on the worldwide fusion program, we note that in burning plasma experiments, such as ITER, a 100 mJ/pulse Doppler-free TALIF diagnostic should be capable of directly measuring the deuterium/tritium (D/T) isotope ratio in the outer 0.5 to 1.0 m of the plasma radius. The D/T ratio is a critically important parameter for the control and optimization of burning plasmas. Therefore, development of the diagnostic system proposed here is also relevant to long-term US participation in diagnostic development for large tokamaks.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Search for Lepton Number Violation in 136 Xe and 134 Xe Decay
The EXO-200/nEXO group at Stony Brook University led by Krishna Kumar searched for neutrinoless double beta decay of 134 Xe and 136 Xe via participation in the final phase of the EXO-200 experiment and calibration pre-R&D for the next generation nEXO concept. On EXO-200, we carried out an improved analysis in the search for 134 Xe using data from Phase-II running. On nEXO, we completed a paper on our first phase of measurements demonstrating the feasibility of using photoelectricity from a gold photocathode to produce controlled amounts of charged clusters in liquid xenon. This has set the stage to develop a new test stand to evaluate the stability of a gold photocathode in order to explore the sensitivity of this method to monitor long electron lifetimes.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Reducing roughness and improving efficiency of MAPbI3 perovskite solar cells made by high-throughput photonic curing
For perovskite solar cells (PSCs) to be commercially viable, the slow and energy-insufficient thermal annealing step must be eliminated. Among the photo-irradiation methods proposed to replace thermal annealing, photonic curing is the fastest conversion method. Photonic curing delivers short (20 μs to 100 ms) but intense light pulses from a broadband (200-1500 nm) xenon flash lamp, making it the only method to convert perovskite under 20 ms. This processing time can be extrapolated to a roll-to-roll web speed of 40 m/min based on laboratory processing conditions. However, most reported PSCs made by photonic curing under 1 second have inferior performance (~10% PCE). Although SEM images show dense and pinhole-free perovskite films, AFM images indicate secondary wavy features of 500 nm-wide ridge and 80 nm-deep trenches on photonically cured perovskite films, the existence of which correlates with poor device performance. We suggest that this morphology feature is produced by volatile solvent evaporation during the fast photonic curing process. Two approaches have been made to remedy this issue: (1) adding CH2I2 as the third solvent in the conventional DMF-DMSO system and (2) applying a controlled air-blowing step before photonic curing to remove excess solvent further. Combining these two approaches produces photonically- cured perovskite films with a comparable film roughness and device performance. Alkyl halide additives have been reported to enhance PSC performance by modulated solvent-solute interactions and C-X (X = Cl, Br, and I) cleavage. Photonic curing can cleave CH2I2, producing disassociated iodide ions to replenish iodine loss induced by photonic curing, which is confirmed by EDX. As a co-solvent, the high boiling point of CH2I2 can also make the solvent less volatile, reducing surface roughness in photonically cured perovskite films. Additionally, photonically-cured perovskite films have longer PL lifetimes and a higher recombination resistance compared to thermally-annealed counterparts. As a result, we demonstrate that photonic curing is a suitable method to replace thermal annealing in high-throughput PSC fabrication.
14 SOLAR ENERGY↗
Examining Nuisance Aerosol Detections in Light of the Origin of the Screening Process (November 2021)
The evolution of philosophy and computations in the International Data Center (IDC) related to aerosol samples have had profound impacts on the number of recorded detections in the network since routine operations began in 2000. Key decisions from policymakers have been the list of triggering radionuclides, the scheme for categorizing these into interest levels 1-5, and an algorithm for determining when an anthropogenic isotope is seen so often that it is no longer interesting, known as the Exponential Weighted Moving Average (EWMA). These are described in the Operations Manual of the IDC. Key parameters that are controlled by the IDC but for which the IDC receives occasional input from policymakers include the constants in EWMA and the peak significance threshold for individual gamma rays, the latter of which directly leads to determination of the presence or absence of a radionuclide in a sample. There are also changes in computations which the IDC makes and informs policy makers about, such as changes in how background is computed, which could also affect the ease of detecting a peak – real or false. Rather than focus on the quantitative changes due to computation changes, this work records some thinking on how isotopes and peak significance levels were chosen, and the resulting detections seen over 18 years during the buildup of the International Monitoring System (IMS). These detections are considered on a global scale to try to determine the relative impact on monitoring, and in some cases, the nature of their existence. Repeated detections of 131I and 133I are the most troublesome, but they are not so frequent to be a major problem for the Verification Regime. These detections could probably be handled adequately using scientific methods currently under development for xenon backgrounds. It is also somewhat problematic that top-level analysis of aerosol backgrounds has not been reported previous to this. The steep increase in the rate of detections after 2016 are a concern, either in the actual backgrounds or from changes in the calculations methods used to generate the Reviewed Radionuclide Report (RRR.) Final conclusions of the authors are that the computational stability of the RRR is very important. With computational stability, changes can be usefully analyzed as being due to changes in radioactivity in Earth’s atmosphere This report is a distillation into text of a talk given in the Radionuclide Experts Group (RNEG) in Vienna during Working Group B (WGB) in February of 2019. This report does not directly contain any IDC data, only summaries by year, or by isotope, or by location. No specific IDC detection by time, location, or isotope is included.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Calibration of the Diffusivity Predictions of Centipede Using Approximate Bayesian Computation and Applications in Nyx (Engineering Scale) and Xolotl-MARMOT (Meso-Scale) Simulations
Fission gas evolution and release in UO 2 nuclear fuel are important fuel performance metrics and occur in several distinct stages: 1) nucleation, growth and resolution of intra-granular bubbles, 2) diffusion to grain boundaries and 3) nucleation and growth of bubbles at grain boundaries, which eventually form a connected network (percolation) enabling release of gas from grain boundaries through connections to triple junctions, grain edges or free surfaces. The NE-SciDAC project is developing several computational tools to model this problem, which are connected in a hierarchical multi-scale framework. The information transfer in the multi-scale framework is a critical step that, in addition to best-estimates, should include uncertainty quantification. Despite taking a first-principles multi-scale approach, there is a need to perform parameter calibration to ensure consistency with available experimental data. In the present study, uncertainty quantification (UQ) and parameter calibration is demonstrated for one of the lower length scale codes in the multi-scale framework (Centipede) and then the results, including instances of the propagated uncertainties, are used in other codes within the framework, specifically Nyx and Xolotl-MARMOT. We calibrated the model parameters in Centipede, a computer code used to predict diffusivities of uranium (U) and xenon (Xe) in the context of the simulation of fission gas in uranium oxide (UO 2 ) nuclear fuel. The Centipede code depends on 183 parameters, all of which are subject to uncertainty. The three data sets used in our calibration effort are taken from the literature. This data is available as a set of measurements, including measurement errors. Our goal is to calibrate a statistical model that predicts both the value of the measurement and the uncertainty associated with the measurement. We perform a Bayesian calibration of the model parameters using a dedicated approximate Bayesian computation (ABC) likelihood function. To avoid excessive computational costs, we replace the expensive Centipede simulation code by a higher-order surrogate model, constructed using only the 9 most important parameters. These important parameters are identified by a preliminary global sensitivity analysis (GSA) study. Among the important parameters are T0 (the temperature at which UO 2 is perfectly stoichiometric) and Hf_pO2 (the temperature dependence of the oxygen (O) partial pressure) that should be considered as operating conditions to be estimated along with the other parameters. We consider two different cases: one where we define one set of these operating conditions for all data sets, and one where we define distinct operating condition parameters for each data set. The Xe diffusivities predicted by the latter case show distinct features that could not be observed in the former. Next, we use the diffusivity predictions by Centipede as input to Nyx, a reduced order fuel performance code focused on gas behavior alone, in order to estimate quantities associated with inter-granular bubble formation at conditions specified by the experiments. Finally, the diffusivities obtained from the calibrated Centipede runs were used in coupled Xolotl-MARMOT simulations of intra- and inter-granular gas evolution. The results are compared to simulations using the baseline diffusivities from Turnbull et al.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Low-Energy Physics in Neutrino LArTPCs
In this white paper, we outline some of the scientific opportunities and challenges related to detection and reconstruction of low-energy (less than 100 MeV) signatures in liquid argon time-projection chamber (LArTPC) detectors. Key takeaways are summarized as follows. 1) LArTPCs have unique sensitivity to a range of physics and astrophysics signatures via detection of event features at and below the few tens of MeV range. 2) Low-energy signatures are an integral part of GeV-scale accelerator neutrino interaction final states, and their reconstruction can enhance the oscillation physics sensitivities of LArTPC experiments. 3) BSM signals from accelerator and natural sources also generate diverse signatures in the low-energy range, and reconstruction of these signatures can increase the breadth of BSM scenarios accessible in LArTPC-based searches. 4) Neutrino interaction cross sections and other nuclear physics processes in argon relevant to sub-hundred-MeV LArTPC signatures are poorly understood. Improved theory and experimental measurements are needed. Pion decay-at-rest sources and charged particle and neutron test beams are ideal facilities for experimentally improving this understanding. 5) There are specific calibration needs in the low-energy range, as well as specific needs for control and understanding of radiological and cosmogenic backgrounds. 6) Novel ideas for future LArTPC technology that enhance low-energy capabilities should be explored. These include novel charge enhancement and readout systems, enhanced photon detection, low radioactivity argon, and xenon doping. 7) Low-energy signatures, whether steady-state or part of a supernova burst or larger GeV-scale event topology, have specific triggering, DAQ and reconstruction requirements that must be addressed outside the scope of conventional GeV-scale data collection and analysis pathways.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗